Fast-acting magnetic switching device for high-level electrical signals and diverter incorporating same

ABSTRACT

A tubular element of magnetizable material is coaxially interposed between inner and outer coaxial conductors so as to be magnetizable to one of two oppositely polarized states depending upon the direction of flow of a low-level DC control current through the inner conductor. A high-level time varying signal applied at one end of the conductors is transmitted to the opposite end thereof, or blocked depending upon whether the induced magnetic field of the signal reenforces the polarity of the magnetizable element or opposes same. A pair of the switching devices included in a pair of circuit paths coupled to a common signal input and arranged such that the flow of control current magnetizes the respective devices to states of mutually opposite polarity, are effective to rapidly divert a signal at the input from one path to the other in response to a reversal of the direction of control current flow.

I United States Patent- Kippenhan I [54] FAST-ACTING MAGNETIC SWITCHING DEVICE FOR HIGH-LEVEL ELECTRICAL SIGNALS AND DIVERTERINCORPORATING SAME [72]" ln ventor: Dean 0. Kippenhan, Castro Valley, Calif. [73] Assignee: The United States A of. America as represented by the United States Atomic Energy Commission [22] Filed: Feb. 4, 1970 [21] Appl.No.: 8,503

[521' U.S. Cl .1 ..307/88 LC, 333/95 R [51] Int. Cl. .L ..I I03k 17/80 [58] Field of Search ..340/l74 S; 307/88 LC;

[5 References Cited UNITED STATES PATENTS 3,479,619. 11/1969 Ngo ..333/31 14 1 Jan. 25, 1972 Primary ExamineF-Stanley M. Urynowicz, Jr. Attorney-Roland A.'Anderson s71 ABSTRACT A tubular element of magnetizable material is coaxially interposed between inner and outer coaxial conductors so as to be magnetizable to one of two oppositely polarized states depending upon the direction of flow of a low-level DC control current through the inner conductor. A high-level time varying signal applied at one end of the conductors is transmitted to the opposite end thereof, or blocked depending upon whether the induced magnetic field. of the signal reenforces the polarity of the magnetizable element or opposes same. A pair of the switching devices included in a pair of circuit paths coupled to a common signal input and arranged such that the flow of control current magnetizes the respective devices to states of mutually opposite polarity, are effective to rapidly divert a signal at the input from one path to the other in response to a reversal of the direction of control current flow.

4 cit-111 s, 3 Drawing Figures ATifNIED JANZSHNZ 3638.032.

:2 "3 i g INVENTOR. a Lk DEAN O. KIPPENHAN HIGH-LEVEL ELECTRICAL SIGNALS AND DIVERTER INCORPORATING SAME BACKGROUND OF THE INVENTION The invention disclosed herein was made in the course of,

or under Contract W-7405-Eng-48 with the United States Atomic Energy Commission.

In various electronic control applications, and elsewhere, it isnecessary to provide for :the rapid switching of high-level electrical signals, especially kilovolt pulses. For example, in the control of an electron induction accelerator a burst of fast rise time, short duration, closely spaced, high level pulses are advantageously employed to trigger thyratrons for effecting energization of magnetic cores along the length of the accelerator in appropriate sequence to accelerate an electron beam pulse traversing same. It is desirable that individual pulses of the control burst be selectively delayable so as to effect mistiming in the energization of the cores and thereby provide a degree of controlover the resultant beam energy. Selective delay may be advantageously accomplished byswitching individual burst pulses between alternative circuit paths'having different time delay characteristics. However, the burst pulses are typically of a level between I and 2 kilovolts, have a duration of a fraction of a microsecond, and are separated by a time interval of about 600 microseconds. Thus, in order to divert an individual pulse from one circuit path to another, the switching mustbe accomplished during the relatively short separation time interval between successive pulses. Although low-level pulses may be readily switched within such a time in- .terval'by solid-state switching circuitry, such circuitry is of course wholly unsuited to the switching of high-level signals.

7 The desired fast switching of high-level pulses may be accomplished by means of coaxial thyratrons; however, the switching system then becomes extremely complex and prohibitively expensive.

i SUMMARY OF THE INVENTION The present invention relates to a fast-acting magnetic switchingdevice which is relatively simple and economical in design, and yet is capable of very rapidly switching high-level electrical signals in response to reversals of the polarity of a low-level DC control current.

The switching device of the present invention generally comprises an elongated conductor, a tubular element of magnetizable material, such as ferrite, coaxially disposed about theconductor, and an outer conductor coaxially disposed about the magnetizable element. The inner and outer conductors are adapted for coaxial connection to a source of highlevel electrical signals, such as fast rise time, short duration,

kilovolt pulses. in addition, means are provided for selectively magnetizing the magnetizable element to one of its two oppositely polarized states, which means are preferably arranged to selectively control the direction of flow of a low-level DC control current through the inner conductor whereby the magnetizable element is magnetized to one polarized state in response to one direction of control current flow, and magnetized to the oppositely polarized state in response to the reverse direction of control current flow. When the polarized state of the magnetizable element is such as to be reenforced by the induced magnetic field of the high-level signal, the inductance presented to the signal is low whereby the signal is transmitted through the switching device. Conversely, when the polarized state of the magnetizable element is such as to be opposed by the induced magnetic field of the high-level signal,

the inductance presented to the signal is high whereby the switching device is impassive to the signal. Thus, switching the magnetizable element from one polarized state to the other is rapidly effected by reversal of the control current to thereby achieve fast switching of the high-level signal.

As another advantageous feature of the invention, the coaxial arrangement of the switching device facilitates manipulation of the high-level signals without significant radiation of In accordance with a particularly important aspect of the invention, a pair of the switching devices may be arranged to provide a fast acting diverter for selectively diverting highlevel electrical signals from one circuit path to another. In this regard, a pair of the switching devices are respectively included in alternative circuit paths coupled to a common signal input. The circuit paths may, for example, terminate in a common output load, such as a thyratron for initiating energization of one of the cores along the beam path of an electron induction accelerator, and one of the circuit paths may be arranged-to impart a predeterminedtime delay to an electrical signal channeled therethrough. The switching devices are simultaneously energized with DC control current directed in such a manner as tomagnetize the respective devices to states of mutually opposite polarity. Consequently, one device is transmissive to the input signal while the other deviceis nontransmissive, and the states of the respective devices are rapidly reversed in response to a reversal of the control current. The input signal may thus be selectively channeled through one circuit path directly, or through the other circuit path with a time delay, to the load by manipulation of the control current.

DETAILED DESCRIPTION OF THE DRAWING the device of FIG. 1; and

FIG. 3 is a schematic diagram of a signal diverter embodying'the switching device of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1 in detail, there is shown a fast-acting magnetic switching device 11, in accordance with the present invention, which generally includes elongated inner and outer coaxially disposed conductors l2 and I3, and a tubular element 14 of magnetizable material, such as ferrite, coaxially interposed between the conductors in insulated relation thereto. More particularly, the inner conductor 12 is preferably covered by a sheath 16 of insulating material, and the element 14 is coaxially disposed about the sheath in close fitting circumscribing relation thereto. To insulate the magnetizable element from the outer conductor 13, an elongated annular sleeve 17 of insulating material is coaxially interposed in close fitting relation therebetween.

Although the magnetizable element 14 may be of integral form, in the interest of utilization of readily commercially available components the element is preferably of articulate construction. In this regard, the element is advantageously comprised of a plurality of magnetizable annular washers, or toroidal magnetic cores 18 of the type extensively employed in computer magnetic core memories, coaxially mounted upon the inner conductor insulating sheath 16 in end-to-end abutment.

The switching device 11 is advantageously adapted for coaxial connection to associated circuitry with which it is to be employed. To this end, a'pair of conventional coaxial connectors 19 are preferably respectively secured to the opposite ends of the inner and outer conductors l2 and 13. More particularly, each connector includes inner and outer connector elements 21 and 22 which are mounted in coaxial insulated relation to each other. The inner connector element 21 is coaxially end secured to inner conductor 12, as by soldering, and the outer connector element 22 is'coaxially engaged by With the switching device 11 constructed in the manner just described, same may be coupled in circuit with, for example, a source of high-level time varying signals such as a high-level pulse source, and .a load, coaxial circuit connection being afforded by the connectors 19. The magnetizable element 14 is magnetized to either of two oppositely polarized states by means subsequently described. In this regard, reference is made to FIG. 2 which depicts a typical hysteresis loop of material employed as element 14. The element may be magnetized to either state x or oppositely polarized state y. When the induced magnetic field of the high-level signal applied to the switching device is such as to reenforce the polarity of the magnetic field intensity H of the magnetized element, the element is driven into saturation in the same direction with little change in magnetic flux density B. For example, assume element 14 is in positively polarized state x, and the applied signal is such as to induce a magnetic field of positive polarity. The positive induced field thus drives the element from state x towards positive saturation point I-I,,, and it is to be noted that the attendant change in flux density B is relatively small. Consequently, the back E.M.F. and associated inductance presented to the applied signal arelow whereby the switching polarized state y, the induced field tends to drive the element from state y towards saturation in the opposite direction, i.e., towards positive saturation point P1,. In this case, the attendant change in flux density B is relatively large. Therefore, the back E.M.F. and inductance presented to the applied signal are very large such that the switching device is nontransmissive to the signal.

It will therefore be appreciated that switching of signals applied to switching device 11 is effected by controlled reversal of the oppositely polarized states of magnetization of the element 14 to selectively render the device transmissive or nontransmissive to the signals. Such magnetization of the element is preferably accomplished by means of a DC control current applied to the inner conductor 12 of the switching device. Depending upon the direction of flow of control current through the conductor 12, element 14 is magnetized to one or the other of the oppositely polarized states x or y. Taking positive current flow as being from left to right, as viewed in FIG. 1, the element 14 is correspondingly magnetized in the clockwise direction, i.e., positive in accordance with accepted conven tion, to state x. Control current flow in the reverse or negative direction from right to left magnetizes the element in the counterclockwise direction, i.e., negatively, to state y. Thus, with a positive signal applied to the switching device, its induced magnetic field is clockwise or positive suchthat it reenforces the magnetization of element 14 when it is in state x, and opposes the magnetization of the element when it is in state y. The device is therefore rendered transmissive to the applied signal in response to positive control current flow, and nontransmissive to the signal in response to negative control current flow in the manner previously described. It should be noted that element 14 is magnetized to either state x or y by a relatively low level of control current which may be rapidly reversed by means of fast acting low-level switching mechanisms, such as a solid-state switching circuit. Of greater significance, the magnetizable element is rapidly switched between states x and y with negligible lag time in response to reversals of the control current to in turn provide fast switching of the applied signal.

Referring now to FIG. 3, it is to be noted that a pair of the switching devices 11 and 11' may be arranged as a fast acting diverter for selectively diverting high-level electrical signals from one circuit path to another. To this end, switching devices 11 and 11 commonly couple a signal input terminal 23 to alternative circuit paths 24 and 26. The inner conducreversable polarity DC control current source 27 and ground in such a manner that the control current flows through the devices in mutually opposite directions with respect to the input terminal. In this regard, when the control current i flows through switching device 11 in a direction towards the input terminal 23, such control current i flows through switching device 11' in a direction away from the input terminal, and vice versa. Thus, with the control current i directed as indicated in FIG. 3, switching device 11 is in magnetized state y and device 11' is in state x. With a signal at input terminal 23 of a polarity such that signal current tends to flow away from the input terminal towards the switching devices, the induced magnetic field due to the signal current opposes the magnetization of device 11, but reenforces that of device 11'. As a result, switching device 11 is nontransmissive to the applied signal while switching device 11' is passive thereto, whereby the signal is diverted to circuit path 26. In response to a reversal of the polarity of control current supplied by source 27, the magnetized states of the switching devices are correspondingly reversed such that device 11 is now passive to the applied signal while device 11 isnontransmissive thereto. Thus, the applied signal is diverted to circuit path 24.

The diverter outlined above is advantageously employed in the manner illustrated in FIG. 3 to selectively apply a signal at input terminal 23, either directly, or after a predetermined time delay, to a load connected to an output tenninal'28. To this end, circuit paths 24 and 26 both terminate at output terminal 28, and one path 26 includes a length of delay line 29, or equivalent time delay element. More particularly, in the preferred arrangement of the diverter, a coaxial T coupler 31 5 is provided with the inner and outer conductors of one arm respectively coaxially connected to one end of the inner and outer conductors of switching device 11, the inner and outer conductors of a second arm respectively coaxially connected to one end of the inner and outer conductors of switching device 11', and the inner conductor of a third arm connected to the input terminal 23. The coupler thus serves to commonly connect the input terminal to switching devices 11 and 11.

A second coaxial T coupler 32 has the inner and outer conductors of one arm coaxially connected to the second end of the inner and outer conductors of switching device 11', the inner and outer conductors of a second arm coaxially connected to the inner and outer conductors of delay line 29, which in the illustrated case is of coaxial configuration, and a third arm connected in a manner subsequently described. The delayline is in turn coupled to a coaxial section 33 having a diode 34 connected in the inner conductor thereof. The inner and outer conductors of such section are coaxially connected to the inner and outer conductors of one arm of a coaxial cross coupler 36, the inner and outer conductors of a second arm of which are coaxially connected to the second end of the inner and outer conductors of switching device 11. The inner conductor of a third arm of coupler 36 is connected to output terminal 28, and a fourth arm of the coupler is connected in a manner subsequently described. The cross coupler thus serves to commonly couple circuit path 24 comprising switching device 11, and circuit path 26 comprising switching device 11', delay line 29, and diode section 33, to output terminal 28. It is to be noted that diode 34 is oriented with its cathode connected to coupler 36, and thus to the output end of switching device 11 and output terminal 28, to thereby prevent applied positive signals transmitted through circuit path 24 to the output terminal from being back channeled through circuit path 26. In addition, the outer conductors of all of the coaxial elements of the diverter are maintained at ground potential by virtue of the ground connection indicated at 37, whereby high-level signals may be manipulated by the diverter without significant radiation of electrical energy and without interaction with extraneous signals. The overall coaxial configuration insures extreme waveform fidelity of the manipulated signals.

Considering now in greater detail the source 27 and a preferred manner of coupling same to the diverter to apply the control-current i to the switching devices 11 and 11', the source preferably includes a conventional solid-state switching circuit 38 of a type capable of rapidly selectively switching low-level current from either of a pair of inputs to an output. One input is connected to the positive terminal of a battery 39, or equivalent DC supply, the negative terminal of which is connected to ground. The second input is connected to the negative terminal of a battery 41, or equivalent DC supply, the positive terminal of which is connected to ground. Thus, the output of the switching circuit may be selectively switched positive or negative. The output of the switching circuit is connected by means of an RF choke 42 to theinner conductor of the fourth armof coaxial cross coupler 36, while an RF choke 43 is connected between the inner conductor of the third arm of coaxial T coupler 32 and ground. Thus, when switching circuit 38 is in a state to couple the positive terminal of battery 39 to choke 42, the control current iflows from the battery to ground through a series circuit path which includes choke 42, the inner conductors of switching devices 11 and 11 and choke 43, in the direction indicated by the arrows in FIG. 3. Thus, the control current renders devices 11 and 11' respectively nontransmissive and transmissive to a positive signal pulse at input terminal 23. The pulse is consequently transmitted through path 26 to the output terminal 28, the RF chokes 43 and 42 being respectively effective in isolating the pulse from ground and the switching circuit 38. Transmission of the pulse to the output terminal is delayed by an amount determined by the delay line 29 included in the circuit path 26.

the negative terminal of battery 41 is coupled to choke 42 whereby the control current iflows from ground to such battery through the previously mentioned series circuit path, i.e., in the opposite direction to that indicated by the arrows in FIG. 3. Although in this case diode 34 tends to be forward biased, the forward resistance is still substantially greater than that. of the circuit path through the inner conductors of devices 11 and l 1', whereby the control current flows through such path rather than through path 26. The respective states of the switching devices are thus responsively reversed whereby device 11 is now transmissive and device 11 nontransmissive to a positive signal pulse at input terminal 23. As a result, the pulse is transmitted through path 24 directly to output terminal 28. RF choke 42 is again effective in isolating the pulse from switching circuit 38.

Thus, in the foregoing manner, the diverter of FIG. 3, is effective to selectively switch pulses at input terminal 23 either directly, or after a predetermined time delay, to output terminal 28.

Although the invention has been hereinbefore'described with respect to what may be considered to be preferred embodiments, it will be appreciated that numerous modifications and variations may be made therein without departing from the true spirit and scope of the invention, and thus it is not intended to limit the invention except by the terms of the following claims. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fast-acting magnetic switching device for high-level electrical signals comprising an elongated inner conductor, a tubular magnetizable element coaxially disposed about said inner conductor, an outer conductor coaxially disposed about said magnetizable element, means for connecting said inner and outer conductors to a source of high-level electrical signals, magnetization means for selectively magnetizing said element to either of two oppositely polarized states, whereby said conductors are transmissive to a signal applied thereto when said element is magnetized to one of said polarized states and nontransmissive to said signal when said element is magnetized to the other of said polarized states, a second tubular ma netizable element coaxially disposed about said mner con uctor, a second outer conductor coaxially disposed about said second magnetizable element, means for coaxially connecting said second inner and outer conductors to said source of high-level electrical signals, second magnetization means for selectively magnetizing said second element to either of two oppositely polarized states, whereby said second inner and outer conductors are transmissive to a signal applied thereto when said second element is magnetized to one of said polarized states and nontransmissive to said signal when said second element is magnetized to the other of said polarized states, means commonly coaxially connecting first ends of said first and second inner and outer conductors to input terminal means for receiving said high-level electrical signals, means connecting said first and second outer conductors to ground, a first circuit path connected to second ends of and including said first inner and outer conductors, and a second circuit path connected to second ends of and including said second inner and outer conductors, said first and second magnetization means being arranged to simultaneously magnetize said first and second elements respectively to ones of said states which are of mutually opposite polarities with respect to said input terminal means, whereby one set of said inner and outer conductols is rendered transmissive to said high-level electrical signals when the other set of said inner and outer conductors is rendered nontransmissive thereto.

2. A device in accordance with claim 1, further defined by said first and second magnetization means comprising a reversible polarity DC control current source, and control circuit means serially connecting said first and second inner conductors between said control current source and ground whereby DC control current from said control current source flows through said first and second inner conductors in mutually opposite directions .with respect to said input terminal means, said control circuit means being arranged to isolate time-varying signals on said first and second inner conductors from said control current source and ground.

3. A device in accordance with claim 2, further defined by said control current source comprising a low-level current switching circuit for selectively switching current flow between either of a pair of inputs and an output, a DC supply having a positive terminal connected to one of said inputs 'of said switching circuit and a negative terminal connected to said second inner conductor to ground.

4. A device in accordance with claim 2, further defined by said first and second circuit paths commonly coupled to output terminal means, said second circuit path including a time delay element and a series diode. 

1. A fast-acting magnetic switching device for high-level electrical signals comprising an elongated inner conductor, a tubular magnetizable element coaxially disposed about said inner conductor, an outer conductor coaxially disposed about said magnetizable element, means for connecting said inner and outer conductors to a source of high-level electrical signals, magnetization means for selectively magnetizing said element to either of two oppositely polarized states, whereby said conductors are transmissive to a signal applied thereto when said element is magnetized to one of said polarized states and nontransmissive to said signal when said element is magnetized to the other of said polarized states, a second tubular magnetizable element coaxially disposed about said inner conductor, a second outer conductor coaxially disposed about said second magnetizable element, means for coaxially connecting said second inner and outer conductors to said source of high-level electrical signals, second magnetization means for selectively magnetizing said second element to either of two oppositely polarized states, whereby said second inner and outer conductors are transmissive to a signal applied thereto when said second element is magnetized to one of said polarized states and nontransmissive to said signal when said second element is magnetized to the other of said polarized states, means commonly coaxially connecting first ends of said first and second inner and outer conductors to input terminal means for receiving said high-level electrical signals, means connecting said first and second outer conductors to ground, a first circuit path connected to second ends of and including said first inner and outer conductors, and a second circuit path connected to second ends of and includiNg said second inner and outer conductors, said first and second magnetization means being arranged to simultaneously magnetize said first and second elements respectively to ones of said states which are of mutually opposite polarities with respect to said input terminal means, whereby one set of said inner and outer conductors is rendered transmissive to said high-level electrical signals when the other set of said inner and outer conductors is rendered nontransmissive thereto.
 2. A device in accordance with claim 1, further defined by said first and second magnetization means comprising a reversible polarity DC control current source, and control circuit means serially connecting said first and second inner conductors between said control current source and ground whereby DC control current from said control current source flows through said first and second inner conductors in mutually opposite directions with respect to said input terminal means, said control circuit means being arranged to isolate time-varying signals on said first and second inner conductors from said control current source and ground.
 3. A device in accordance with claim 2, further defined by said control current source comprising a low-level current switching circuit for selectively switching current flow between either of a pair of inputs and an output, a DC supply having a positive terminal connected to one of said inputs of said switching circuit and a negative terminal connected to ground, and a second DC supply having a negative terminal connected to the other of said inputs of said switching circuit and a positive terminal connected to ground, said control circuit means comprising an RF choke connecting said output of said switching circuit to said second end of said first inner conductor, and a second RF choke connecting said second end of said second inner conductor to ground.
 4. A device in accordance with claim 2, further defined by said first and second circuit paths commonly coupled to output terminal means, said second circuit path including a time delay element and a series diode. 